Alpha 1-antitrypsin (.alpha.1AT).sup.3 deficiency, one of the more common lethal hereditary disorders in Caucasians of European descent, is characterized by reduced serum levels of .alpha.1AT, a 52-kD glycoprotein that functions as an antiprotease. The deficiency state is caused by mutations of the .alpha.1AT gene, a pleiomorphic, 12.2-kb 7-exon gene. Normal .alpha.1AT serum levels are 20-53 .mu.M; various combinations of at least 17 different mutations of the .alpha.1AT gene are associated with an .alpha.1AT level &lt;11 .mu.M and significant risk for developing emphysema. A subset of mutations is associated with hepatitis and cirrhosis. These latter mutations all involve the production of abnormal proteins: they do not include null mutations. The pathogenesis of the liver disease is thought to be due to the accumulation of an abnormal .alpha.1AT protein in hepatocytes, and is associated with the finding that certain mutations of the .alpha.1AT gene cause derangement in the protein's intracellular processing and defects in the protein's excretion, commonly associated with liver injury. The molecular defect in the protease inhibitor (Pi)Z allele, the allele most commonly associated with liver injury, is a G to A transition resulting in a Glu to Lys substitution at amino acid 342. This mutation is thought to cause the variant protein to aggregate in the rough endoplasmic reticulum of the liver cells.
In the field of gene therapy, "gene replacement" is a useful approach. "Gene replacement" refers to the replacement of a mutated genetic element with a normal gene.
Ribozymes are RNA molecules which have the ability to cleave RNA sequences at specific sites. The hammerhead ribozyme motif, first identified in the self-splicing activity of a plant RNA virus, cleaves the phosphodiester bond downstream of a GUX triplet, where X can be C, U, or A. Target specificity for this cleavage can be achieved by flanking the hammerhead ribozyme motif with antisense sequences, complementary to the target RNA. Ribozymes have been targeted to a wide variety of substrates and tested in biological systems to achieve the inhibition of cellular gene expression or viral replication.
There is a need for providing improved methods of gene replacement therapy. There is a need for compositions and methods for treating individuals who have alpha 1-antitrypsin deficiency.